Outside mirrors having indicia for signaling turns or alerting a driver to vehicles in the driver's blind spot are well known in the art. Side blind zone alert (SBZA) systems often use an icon that appears in the vehicle's side mirror when the system detects a vehicle or other objects in the driver's blind spot. In use, the SBZA enables the vehicle to detect other vehicles located where they may be difficult for the driver to directly see using the outside mirrors.
When the SBZA system detects a vehicle in the adjacent lane, the system will illuminate a symbol or other indicia on the driver's outside rearview mirror. This alerts the driver to a potential collision. Often, when the driver activates the turn signal in the direction of the detected vehicle, the blind spot alert symbol will flash to better draw the attention of the driver. Otherwise, the symbol remains illuminated until the other vehicle has left the blind zone. Prior art FIG. 1A, FIG. 1B and FIG. 1C illustrate various types of indicia that are often used with the outside rearview mirror. FIG. 1A illustrates a mirror assembly 100A that uses a triangular symbol 103A positioned at a side edge of mirror 101A. The triangular indicia 103A is commonly used with the SBZA for indicating a detected vehicle in the vehicle's blind spot zone.
Similarly, FIG. 1B illustrates a mirror assembly 100B that shows vehicle indicia 103B that depicts two offset vehicles such that one vehicle is to the left and behind the driver's vehicle in the blind spot zone. The vehicle indicia 103B is also positioned on a side of the mirror 101B and is also used in connection with an SBZA. Finally, FIG. 1C is another mirror assembly 100C that is used as a turn signal indicator such as the chevron 103C that is positioned at an edge of the mirror 101C. When used in this type of application, the chevron 103C would be used with the driver's outside mirror showing the indicia depicting a turn to the left while blinking or illuminated. These indicia or other symbols are most often cut or etched into the mirror glass however indicia formed using microdots and associated applica are also possible. When activated, light projected behind the mirror element will illuminate the symbol or indicia such that it is visible for altering the driver.
Various lighting packages have been developed in order to provide illumination to the indicia behind the mirror glass. The illumination allows the indicia to be easily detected by the driver in both daylight and darkness. Since the outside mirror housing must be limited to a certain size, the optics for lighting the symbols and other indicia become very important since they must radiate a bright light while still remaining a relatively small size in order to fit within a predefined space.
FIG. 2 is a prior art cross-sectional diagram showing a lighting technique as used in the prior art. The optical module 200 includes a printed circuit board (PCB) 201 having a light emitting diode 203 mounted on one side of the PCB. An optical device 205 is positioned in front of the LED 203 and is used for gathering and directing light rays at a specific angle towards the indicia. This allows the indicia to be visible to the user. In order to protect the optics within the optical module, a cover 209 is used to surround the back portion of the module.
The optic device 205 comprises a first lens surface having a total internal reflector (TIR) portion surrounding a refractive portion and a macro beam shaping device. Rather than incorporating lenses into the design, TIR optical materials are used for obtaining a desired illumination pattern from the LEDs or other illumination devices. TIR optical material is advantageous since it can be manufactured of plastic of a reduced size and weight. Moreover, the TIR material can encompass an entire light source for reducing and/or eliminating optical loss that would occur with an optical lens. As seen in FIG. 2, the TIR optic 205 uses surfaces of revolution based on free-form curves such as a light collection cup 207. The TIR optic 205 also uses other optical principles such cubic splines or Bézier curves that operate to steer and/or direct light in a desired direction.
Those skilled in the art will recognize that other embodiments may use an eccentric reflector to reflect the maximum amount of light from the light source toward the indicia. An eccentric reflector is a reflector that reflects light at a point which is not at a focal point of the reflector optic. However, a disadvantage of these types of lighting assemblies is that the use of eccentric reflectors and other optical devices increase the overall thickness of the lighting module. Although thin profile designs can be achieved using both LED backlighting techniques and eccentric reflectors, current design parameters often require a depth or thickness less than 9 mm. Accordingly, designs using an eccentric reflector can be limited to applications where these types of design constraints are not an issue and the mirror can accommodate the large size of this type of lighting assembly.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.